Who makes the call of where the "point of supply" starts, in the Act, section 3, there is the Point of Supply definitions, defining where the POS begins, which is fine but does it ever get recorded/noted anywhere that the POS for a property is......? Otherwise it can get confusing of where the POS starts.
Next part of the question, if the berm transformer for this property (located 50 odd metres from the boundary) has a NE link on the LV side and also 5 x Dist fuses that supply 5 x Dist Cabinets complete with Main switches, each DC then supplies a building of multiple lockup units (each unit has its own swb). Is this setup regarded as one installation if the POS is the LV side of the TX or if the POS is at each Dist Cabinet is this regarded as 5 installations?
Therefore is each DC regarded as a Main Switchboard , as each cabinet does control a building?
Point of Supply
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gregmcc
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Re: Point of Supply
does each DC have it's own N&E busbars, an MEN link and an main earthing system?
Is each DC for exclusive use of an installation?
Who own the DC - the property owner? the network company?
Is each DC for exclusive use of an installation?
Who own the DC - the property owner? the network company?
Re: Point of Supply
Hi Greg, I have only seen the reticulation schematics, the D/cabinets are metal so I assume there will be N & E bar with a link but there are definitely no earth conductors on any incoming or outgoing cables.
The 5 x Dc's will be owned by the property owner, each DC is exclusive to a building containing lockup units, each unit has their own switchboards and earthing system.
I have seen this setup many times but still wonder if it is correct.
The 5 x Dc's will be owned by the property owner, each DC is exclusive to a building containing lockup units, each unit has their own switchboards and earthing system.
I have seen this setup many times but still wonder if it is correct.
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gregmcc
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Re: Point of Supply
This could be private works, I would be talking to the designer as you would seem to need a defined point where it changes from works to installation just so it's plain and clear to everyone and from there you can make the determination on how things are going to work.
I'm not exactly sure but if they are designed as private works there may be some extra hoops to jump thru - A safety management plan??
If you decide that the cabinets are to be installation (main switchboards) then they must contain all the things that make them a main switchboard, N+E bars, main switch, main earthing system etc...
I would be pushing the designer for a certified design, that way it pushes the responsibility for electrically safe and compliant on to the designer, as we all know some designers are not very good at designing and push the technical and compliance back to the electrician to sort out as well as keeping to the design - which we know can be difficult.
I'm not exactly sure but if they are designed as private works there may be some extra hoops to jump thru - A safety management plan??
If you decide that the cabinets are to be installation (main switchboards) then they must contain all the things that make them a main switchboard, N+E bars, main switch, main earthing system etc...
I would be pushing the designer for a certified design, that way it pushes the responsibility for electrically safe and compliant on to the designer, as we all know some designers are not very good at designing and push the technical and compliance back to the electrician to sort out as well as keeping to the design - which we know can be difficult.
Re: Point of Supply
Exactly, engineers are very reluctant to put their name to a certified design, in my past experience they generally tell the electrician just to sign the b...... COC or the project wont get signed off, so then the Main Contractor or owner also start putting pressure on the electrician.
I believe in a situation/design like this, the engineer should have to state what parts of the installation are what, not up to the electrician.
I believe in a situation/design like this, the engineer should have to state what parts of the installation are what, not up to the electrician.
Re: Point of Supply
Agree it can be difficult to determine where the POS is.
The question is why we need to know the POS in the first place; and that comes down to determining things like which is the MSB.
Most of what depends on identifying the PoS relates to 'compliance' rather than "safety".
So I believe the main thing is to apply the rules consistently.
In this case there's no suggestion that the property has been subdivided; so it's all one "property".
That means that, on a straight reading from definition of POS in Act, there's only one location for PoS; and it is where the fittings (including conductors) start being "exclusive fittings" supplying that property (option (b)).
"Exclusive fittings" is about function rather than ownership.
The only "ownership" that matters is who owns the tx; because option (a) of the definition only applies for a network-owned tx located within the property. Which means that if it's not a network-owned tx, then the POS is where the incoming HV supply crosses the boundary.
Assuming the tx is owned by the network; then
- if tx is within property, then first "exclusive fittings" are the LV fuses ;
- if tx is outside property, first 'exclusive fittings" is where the LV conductors from those fuses cross the boundary.
Which means that there is not just one PoS, but 5; all located pretty much together.
It follows that there are 5 installations, each one including a DC.
Two options within that scenario
- treat the DCs as MSB for each installation, c/w MEN, and MEC to electrode, and overcurrent protection for outgoing submains.
- treat them as simply 'fittings associated with mains";equivalent to a domestic meterbox or mains entry box, with the MSB being within the building
But as it seems each DC will have a number of circuits, one to each individual occupancy swbd within the relevant building;
then clearly these are submains (not mains); and the DC has to be the MSB.
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The alternative view would be - as Greg suggested - that there's an aspect of "private works".
But from the description each DC only supplies one building, so difficult to make a case that they are part of a distribution network.
So I don't think the 'private works' theory can be applied in this case.
Where that can come in is where there's something like "rising mains" with tee-offs distributing power to multiple occupancies that are in different "properties".
So if instead of 5 fuses each feeding 1 x DC, the tx had only one outgoing supply looped to all 5 x DCs; then you'd have to be thinking in terms of private works.
You can have multiple installations on one property, and you can also have a single installation that has more than one PoS.
But for each feed-in from network, for a new installation, there can really be only one installation on any property.
Remember the rule that wiring for different installations can't be in same wiring system [3.9.8.2].
Where there is an option, then whichever option is chosen has to be applied to all aspects of the design.
Problems arise when people try to have a bob each way, and apply the rules inconsistently.
Or don't think about it at all, and just copy arrangements that used to be widely accepted practice but no longer comply with today's rules.
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Clearly there's a plan already, and it is all but certain that it meets the requirements for being a certified design [as per ESR 58 (1)].
So no need to ask for one, you already have it - and can rely on it.
The reluctance of designers to sign the old "declaration of conformity" for their designs is the reason the certified design concept was introduced (in 2013 amendment).
All you have to do is follow it, and attach a copy to your CoC.
That way even if it's non-compliant, you'll be off the hook
The question is why we need to know the POS in the first place; and that comes down to determining things like which is the MSB.
Most of what depends on identifying the PoS relates to 'compliance' rather than "safety".
So I believe the main thing is to apply the rules consistently.
In this case there's no suggestion that the property has been subdivided; so it's all one "property".
That means that, on a straight reading from definition of POS in Act, there's only one location for PoS; and it is where the fittings (including conductors) start being "exclusive fittings" supplying that property (option (b)).
"Exclusive fittings" is about function rather than ownership.
The only "ownership" that matters is who owns the tx; because option (a) of the definition only applies for a network-owned tx located within the property. Which means that if it's not a network-owned tx, then the POS is where the incoming HV supply crosses the boundary.
Assuming the tx is owned by the network; then
- if tx is within property, then first "exclusive fittings" are the LV fuses ;
- if tx is outside property, first 'exclusive fittings" is where the LV conductors from those fuses cross the boundary.
Which means that there is not just one PoS, but 5; all located pretty much together.
It follows that there are 5 installations, each one including a DC.
Two options within that scenario
- treat the DCs as MSB for each installation, c/w MEN, and MEC to electrode, and overcurrent protection for outgoing submains.
- treat them as simply 'fittings associated with mains";equivalent to a domestic meterbox or mains entry box, with the MSB being within the building
But as it seems each DC will have a number of circuits, one to each individual occupancy swbd within the relevant building;
then clearly these are submains (not mains); and the DC has to be the MSB.
-------------
The alternative view would be - as Greg suggested - that there's an aspect of "private works".
But from the description each DC only supplies one building, so difficult to make a case that they are part of a distribution network.
So I don't think the 'private works' theory can be applied in this case.
Where that can come in is where there's something like "rising mains" with tee-offs distributing power to multiple occupancies that are in different "properties".
So if instead of 5 fuses each feeding 1 x DC, the tx had only one outgoing supply looped to all 5 x DCs; then you'd have to be thinking in terms of private works.
You can have multiple installations on one property, and you can also have a single installation that has more than one PoS.
But for each feed-in from network, for a new installation, there can really be only one installation on any property.
Remember the rule that wiring for different installations can't be in same wiring system [3.9.8.2].
Where there is an option, then whichever option is chosen has to be applied to all aspects of the design.
Problems arise when people try to have a bob each way, and apply the rules inconsistently.
Or don't think about it at all, and just copy arrangements that used to be widely accepted practice but no longer comply with today's rules.
---------------
Clearly there's a plan already, and it is all but certain that it meets the requirements for being a certified design [as per ESR 58 (1)].
So no need to ask for one, you already have it - and can rely on it.
The reluctance of designers to sign the old "declaration of conformity" for their designs is the reason the certified design concept was introduced (in 2013 amendment).
All you have to do is follow it, and attach a copy to your CoC.
That way even if it's non-compliant, you'll be off the hook
Re: Point of Supply
Nicely explained Alec
The electrical engineer drawings are typical schematics, ie identifies location, date drawing designed and by whom, date checked and by whom, but no standards referenced.
Last time a similar design was used and the electrician referenced it was a certified design on the COC, the engineer was not happy and demanded that the COC was changed and the certified design section removed from the COC.
I agree and think the DC's are Main Swbs, as they have a Main switch that controls a building, o/load protection and N and E bars (metal cabinets). What I believe is wrong, is that the outgoing cables to each tenancy (in the same bldg) do not have earth conductors, they all have an MEN swbs with earth electrodes, this design has been used before and I have mentioned this previously on the forum.
The electrical engineer drawings are typical schematics, ie identifies location, date drawing designed and by whom, date checked and by whom, but no standards referenced.
Last time a similar design was used and the electrician referenced it was a certified design on the COC, the engineer was not happy and demanded that the COC was changed and the certified design section removed from the COC.
I agree and think the DC's are Main Swbs, as they have a Main switch that controls a building, o/load protection and N and E bars (metal cabinets). What I believe is wrong, is that the outgoing cables to each tenancy (in the same bldg) do not have earth conductors, they all have an MEN swbs with earth electrodes, this design has been used before and I have mentioned this previously on the forum.
Re: Point of Supply
Starting from the DCs being MSBs (as I believe they should be); then the outgoing circuits are submains.
If there was just one such submain, the building could be treated as an outbuilding, and the submain could have a PEN conductor and no PEC.
As per 5.5.3.1, option (b).
But that's only OK for a single supply to the outbuilding; as condition (i) says there can only be one MEN in any outbuilding.
With multiple supplies; the submains must all have PECs.
So, not compliant - but still it's a certified design.
The schematic by itself may not be, since it contains no stipulation as to Standards.
But the combination of terms of contract plus schematic cited in the contract add up to a CD.
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Only other interpretation is that swbds for individual occupancies are MSBs for a bunch of separate installations within one structure.
Following that approach; the conductors from DC to each swbd are "mains" and the PoS for each is within the relevant DC.
However (as explained earlier), I believe this can only fit the Act if each occupancy is a fully subdivided "property".
The definitions of property specifically states that for unit titles, the "property" is the entire property within the land boundary, and not an individual unit title. So it certainly can't be a mere licence to occipy (tenancy agreement).
Not that there's anything particularly unsafe about this; provided the occupancies are not sharing any earthing fittings.
But in my view definitely not compliant with Act & ESRs
But once again the documentation overall must add up to a certified design; which allows responsibility for compliance to be passed to the designer.
But the CD process provides us with bum-cover.
And it is unlawful for anyone to be forced, by contract, to break the law eg by issuing a false CoC.
If there was just one such submain, the building could be treated as an outbuilding, and the submain could have a PEN conductor and no PEC.
As per 5.5.3.1, option (b).
But that's only OK for a single supply to the outbuilding; as condition (i) says there can only be one MEN in any outbuilding.
With multiple supplies; the submains must all have PECs.
So, not compliant - but still it's a certified design.
The schematic by itself may not be, since it contains no stipulation as to Standards.
But the combination of terms of contract plus schematic cited in the contract add up to a CD.
--------------
Only other interpretation is that swbds for individual occupancies are MSBs for a bunch of separate installations within one structure.
Following that approach; the conductors from DC to each swbd are "mains" and the PoS for each is within the relevant DC.
However (as explained earlier), I believe this can only fit the Act if each occupancy is a fully subdivided "property".
The definitions of property specifically states that for unit titles, the "property" is the entire property within the land boundary, and not an individual unit title. So it certainly can't be a mere licence to occipy (tenancy agreement).
Not that there's anything particularly unsafe about this; provided the occupancies are not sharing any earthing fittings.
But in my view definitely not compliant with Act & ESRs
But once again the documentation overall must add up to a certified design; which allows responsibility for compliance to be passed to the designer.
But the CD process provides us with bum-cover.
And it is unlawful for anyone to be forced, by contract, to break the law eg by issuing a false CoC.
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Re: Point of Supply
I love the CD argument that you can get into with engineers. While a CD provides a bum cover for the electrician, the designer is still liable if the design isn't a certified design. Regulation 14 spells this out and its not an offence for being unsafe, rather an offence for not being safe! Therefore non-compliance comes into it as well.
Re: Point of Supply
The offence of something being "not electrically safe" comes directly from the requirement for that something to be "electrically safe".
"Electrically safe" and "electrically unsafe" are not opposites, it's not an either / or choice where something is one or the other.
As defined in ESR 5, they are two points - with a gap between them - on a scale of safety that extends beyond these two points in both directions.
I guess the lower end of the scale might be called "immediately lethal", and the upper end "no risk whatsoever".
"Electrically safe" is the required level of safety when we do PEW (ESR13), or design things(ESR 14);
so the offence - in both cases -is failing to reach that level.
"Electrically safe" and "electrically unsafe" are not opposites, it's not an either / or choice where something is one or the other.
As defined in ESR 5, they are two points - with a gap between them - on a scale of safety that extends beyond these two points in both directions.
I guess the lower end of the scale might be called "immediately lethal", and the upper end "no risk whatsoever".
"Electrically safe" is the required level of safety when we do PEW (ESR13), or design things(ESR 14);
so the offence - in both cases -is failing to reach that level.
Re: Point of Supply
This topic came up again in discussion the other day, if the POS was the Dist Cabinets does that mean if these cabinets required work on them in the future eg replacing fuse holders is that on the Network?
Re: Point of Supply
Probably
Same as a supply fuse; whether it's up a pole, in a pit, or in a pillar.
It's "exclusive fittings".
PoS can't be upstream of the first "exclusive fittings";
but if those fittings are outside the property boundary for the installation, the PoS will be downstream ; eg for a normal house it's where cables from exclusive fittings cross the boundary.
The PoS is usually but not always part of the network; however can instead by part of private works.
Same as a supply fuse; whether it's up a pole, in a pit, or in a pillar.
It's "exclusive fittings".
PoS can't be upstream of the first "exclusive fittings";
but if those fittings are outside the property boundary for the installation, the PoS will be downstream ; eg for a normal house it's where cables from exclusive fittings cross the boundary.
The PoS is usually but not always part of the network; however can instead by part of private works.
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